This invention relates to methods of heating and/or homogenizing of liquid products in a steam-liquid injector. By liquid products (hereinafter: products) are meant liquids with different degrees of viscosity, with or without solid particles (solid phase) dispersed in them. By a steam-liquid injector is meant an injector which uses steam as a process medium and liquid as injected medium.
The prior art methods of heating and/or homogenizing of products in a steam-liquid injector include the following steps:
feeding steam and a product into a mixing chamber--through a steam nozzle and a product nozzle accordingly; PA0 forming in the mixing chamber a two-phase steam-liquid flow by mixing the product with steam; PA0 compressing the two-phase steam-liquid flow and condensing steam in the product. PA0 [1] WO 89/10184, also published as EP 0399041, describes an emulsifier based on a passive steam-liquid injector; PA0 [2] SU 1472052 describes a method of liquid foodstuff heating in a steam-liquid injector; PA0 [3] SU 1281761 describes a water-heating steam-liquid injector. PA0 [4] SU 1507299 describes a pasteurization method for a liquid whole milk substitute in a passive supersonic steam-liquid injector, PA0 [5] U.S. Pat. No. 5,205,648 and [6] U.S. Pat. No. 5,275,486 &lt;&lt;Method and Device for Acting upon Fluids by Means of a Shock Wave&gt;&gt; describe, as an instance of application, heating and homogenizing of liquid foodstuffs in a steam-liquid injector, wherein product and steam are fed to the mixing chamber at a subsonic speed, creating a two-phase steam-liquid mixture; in the process the mixture is first sped up to the sonic and then to a supersonic speed and, due to a shock wave, transformed into a single-phase liquid flow traveling at a subsonic speed. PA0 [7] U.S. Pat. No. 5,544,961 &lt;&lt;Two-Phase Supersonic Flow System&gt;&gt; describes, as an instance of application, heating and homogenizing of liquid foodstuffs in a steam-liquid injector, with product fed to the mixing chamber at a subsonic speed and steam fed at a supersonic speed, creating a two-phase steam-liquid mixture traveling at a supersonic speed; in the process the two-phase steam-liquid flow, due to a shock wave, is transformed into a single-phase liquid flow traveling at a subsonic speed. PA0 [7] U.S. Pat. No. 5,544,961 &lt;&lt;Two-Phase Supersonic Flow System&gt;&gt; describes, as an instance of application, heating and homogenizing of liquid foodstuffs in a steam-liquid injector, with product fed to the mixing chamber at a subsonic speed and steam fed at a supersonic speed, creating two-phase steam-liquid mixture traveling at a supersonic speed; in the process the two-phase steam-liquid flow, due to a shock wave, is transformed into a single-phase liquid flow traveling at a subsonic speed. PA0 [8] [M. Rogenhofer, E. Hauss, V. Fisenko &lt;&lt;Aufbau und Wizkungsweise einer neuen multifunktionalen Uberschall-Direktdampf-Technologie (Transsonic-Gerat) fur den Milch-und-Lebensmittelbereich&gt;&gt;].
Examples of the use of this method and devices based thereon can be found in the following patents:
Some distinctive features of the method and device suggested by the above patent provide for a more stable operation of the injector, a higher shock wave and a higher degree of sterility and homogeneity of the product.
From the points of the essence of the present invention, the number of common features and the objects in view, its closest prototype is the method and device described in an article [8] under the title &lt;&lt;The Principle and the Use of a New Multifunction Direct Steam Technology (Ultrasonic Device) in Food and Dairy Industry&gt;&gt; by M. Rogenhofer, E. Hauss and V. Fissenko, published in &lt;&lt;Magazine for Food and Dairy Industry&gt;&gt; # 13/114, Mar. 25, 1993).
According to the authors of the above article, the injector described in their article was based on U.S. Pat. No. 5,205,648 [5] and U.S. Pat. No. 5,275,486 [6].
Based on testing operating conditions given in the article, it can be presumed that under some regimes (according to steam pressures forward of the injector and inside the mixing chamber) the steam was fed to the mixing chamber at a supersonic speed. In other words, in such cases the injector operated according to U.S. Pat No. 5,544,961 [7]. This enables us to consider the results according to several patents simultaneously.
The test data reported in the above article demonstrate that the required homogenizing standards have not been achieved whereas the pasteurization quality corresponds to that achieved on conventional equipment at an appropriate temperature. From FIG. 5 and information contained in the article [8], it can be seen that the stability of the injector's operation decreases sharply with the increase in the injection index, i.e. with reduction of the product's temperature difference between the inlet and the outlet of the injector. In all the above analogs and prototypes all the essential features, both of methods and devices, are related to conditions of steam feeding to the mixing chamber, proportions between the dimensions of the steam nozzle channel and the mixing chamber, and the effect of these parameters on the injector's operation. The device's longitudinal section given in FIG. 2. in the article.[8] and description of its operation demonstrate that the product nozzle's critical section area is sufficiently large to allow a relatively low speed of product at the point where it is mixed with The steam. The fact that the device works as a passive injector suggests a low speed of product. Likewise, in other designs or design and calculation instructions for injectors no importance is attached to the flow speed in the mixing area. For instance: [9] Y.Y. Sokolov and N. M. Zinger, &lt;&lt;Stream Devices&gt;&gt;, Moscow, &lt;&lt;Energhia&gt;&gt;, 1970, pp. 234-251.
The stability of the injector's operation, especially at the moment of start and in transient condition, remains one of the main problems of the prior art injector systems.
Accordingly, they require highly skilled maintenance staff especially start up men. As a result, the injectors are perceived as unreliable and unpredictable devices which restricts their application despite their many advantages